An Alternative Lifetime Model for White Light Emitting Diodes under Thermal⁻Electrical Stresses

Area of Science:

• Materials Science
• Electrical Engineering
• Reliability Engineering

Background:

• Accelerated degradation testing (ADT) is crucial for predicting the lifespan of white light emitting diodes (LEDs).
• Conventional ADT methods often rely on single stress factors, limiting prediction accuracy.
• Accurate lifetime prediction is essential for the reliability of LED applications.

Purpose of the Study:

• To propose a novel lifetime model for LEDs that incorporates both thermal and electrical stresses.
• To enhance the accuracy of lifetime prediction by utilizing junction temperature and driving current as key input parameters.
• To address the limitations of single-stress ADT methods in LED reliability assessment.

Main Methods:

• Developed a new lifetime model by integrating LED lifetime features and lumen depreciation laws under dual stresses.
• Utilized junction temperature as a more reliable thermal stress indicator compared to ambient temperature in conventional ADT.
• Employed driving current as the electrical stress parameter.

Main Results:

• The proposed model effectively predicts LED lifetime under combined thermal and electrical stresses.
• Junction temperature proved to be a more reliable thermal stress parameter than ambient temperature.
• Case studies demonstrated the model's practicality and general applicability across different LED products.

Conclusions:

• The novel lifetime model provides a more accurate and reliable method for predicting LED lifespan.
• Dual-stress ADT, considering both thermal and electrical factors, is superior to single-stress approaches.
• Electrical stress plays a significant role in LED degradation and must be considered alongside thermal stress for comprehensive lumen decay analysis.